Elevator control system



Jan. 11, 1955 w. H.YBRUNS ELEVATOR CONTROL SYSTEM Fi l ed June 14. 1952v s She'ets-Sheet 1 I Ill /I/I V/l a we pHLT

mm DHL W/Lt/AM HEMP) Bel/N5 INVENTOR BY fix aawu ATTORNEY Jan. 11, 1955w. l-1.BRUN$ 2,699,226

- ELEVATOR CONTROL SYSTEM Filed June.l4. 1,952 7 5 SheetsSheet 2 AC5 AC6Q CFMA FRTI ' FRA 1 FRPSI FRFZ RFA- FH WILLl/IM HENEVBPUNS INVENTOR BYATTORNEY Jan. 11, 1955 w. H. BRUNS 2,699,226;

ELEVATOR CONTROL SYSTEM Filed June 14. 1952 5 Sheets-Sheet 4 BY ATTORNEYUnited States Patent ()1 ELEVATOR CONTROL SYSTEM William Henry Bruns,Lincolndale, N. Y., assignor to Otis Elevator Company, New York, N. Y.,a corporation of New Jersey Application June 14, 1952, Serial No.293,604

11 Claims. (Cl. 187--29) The invention relates to control systems formovable bodies, especially systems for controlling the operation ofelevator cars.

In the control of an elevator car, a great many of the operationsinvolved depend on the position of the car in the hoistway, especiallywith relation to the floors at which stops are to be made. Mechanism isprovided for effecting such control operations and is usually located inthe pent house and driven from the elevator car. Such mechanisms havebeen termed selectors or in some cases floor controllers. Among theoperations controlled by such mechanisms as applied to a system in whichthe car stops automatically at floors for which calls are registered arethe picking up of the calls, lighting of hall lanterns, initiating slowdown of the car at floors at which calls are picked up, automaticcancellation of calls as they are answered, direction set up, reversalat farthest call, acceleration and retardation of the elevator car andoperating car position indicators. In view of these and other operationssubject to the selector mechanism, a considerable amount of apparatus isinvolved.

It is the object of the invention to provide an elevator control systemutilizing control mechanism of the above character which is of simpleconstruction, economical to manufacture and install, and in whichvarious control oplerations are effected electrically instead ofmechanica y.

The invention involves the utilization of a voltage difference between avoltage representing the actual position of the car in the hoistway anda voltage related to the floors served by the car for effecting theactuation of control mechanisms for performing various selectoroperations.

In carrying out the invention in accordance with the embodiment whichwill be described, as applied to effecting certain operations dependenton the exact position of the car, as for example for operating a carposition indicator, the voltage difference is that between the carposition voltage and a floor reference voltage and this voltagedifference is utilized to cause the floor reference voltage to be inaccordance with car position. As applied to effecting operations whichtake place in advance of the car, such as picking up and automaticallycancelling calls, lighting hall lanterns at floors at which stops are tobe made, initiating slow down and controlling retardation, a biasingvoltage is added to cause the reference voltage to represent a positionin advance of the car.

The car position voltage is taken off a potentiometer, the slider ofwhich is actuated in accordance with the movement of the elevator car.This potentiometer serves as a master potentiometer. The floor referencevoltage also is taken off a potentiometer connected in bridgerelationship to the car position (master) potentiometer. The position ofthe slider of the floor reference potentiometer is determined by thevoltage diiference existing across the diagonal of the bridge connectingthe two sliders. The advance voltage is taken off a separatepotentiometer, also connected in bridge relationship to the masterpotentiometer. The slider of this advancer potentiometer is advancedwith respect to the slider of the car position potentiometer by abiasing voltage superimposed in the bridge diagonal circuit. The floorreference and advancer potentiometers are in the nature of slavepotentiometers. The sliders of the slave potentiometers are driven bymotors subject to the voltages of their respective bridge diagonalcircuits. In the arrangement illustrated the potentiometers areconnected across alternating current supply lines and the resultantvoltage of the bridge diagonal is amplified and applied to the slavepotentiometer actuating motor. Where voltage exists between the twosliders the motor actuates the slider of the slave potentiometer in adirection determined by the phase of the diagonal voltage to reduce thisvoltage to zero, whereupon the motor comes to a stop.

One feature of the invention is to provide on a slave potentiometer,points representative of the floors served by the car and to providevoltage differences between such points in accordance with the heightsof the floors which they represent.

Another feature of the invention is to limit the amount of advancemovement of the slider of the advancer potentiometer for full speedoperation and to cause less advance to take place on shorter runs wherefull speed is not attained.

Still another feature of the invention is, when a call for a floor ispicked up, to provide a voltage across the diagonal of the advancerbridge which accurately meas ures the distance of the car from the floorat which the stop is to be made.

Another feature is the utilization of this accurate voltage differenceto determine on full speed runs the point at which retardation of theelevator hoisting motor begins and on runs of less than full speed thepoint at which acceleration of the elevator hoisting motor isdiscontinued.

Still another feature is the utilization of this accurate voltage fordistance control of the retardation of the car.

Other features and advantages of the invention will be apparent from thefollowing description and appended claims.

In the drawings:

Figure 1 is a simplified schematic representation of an elevatorinstallation in accordance with the invention;

Figures 2, 3, 4 and 5 taken together constitute a simplified wiringdiagram of the circuits for the elevator installation of Figure 1; and

Figure 6 is a key sheet showing the electromagnetic switches in spindleform.

For a general understanding of the invention reference may be had toFigure 1, wherein is illustrated by way of example an elevatorinstallation in which the car serves five floors. The floors aredesignated generally as L and differentiated by appended referencecharacters. The car is raised and lowered by means of an electrichoisting motor 10, which motor drives a traction sheave 11 over whichpass hoisting ropes 12 for the car 13 and counterweight 14. Current forthe motor is provided by a variable voltage generator of a motorgenerator set 15. An electromechanical brake BR is provided and isapplied to effect the stopping operation and to hold the car when atrest.

The car position potentiometer CP is driven preferably by means of atape 16 attached to the car and counterweight and having teeth thereonfor engaging teeth on the potentiometer driving Wheel. Thispotentiometer may be in the form of a helix with its slider arranged tomove in a helical path as is well understood. The floor referencepotentiometer FRP will be described as controlling a car positionindicator 17 and as such may be located at the first floor as indicated.Two advancer potentiometers are utilized, one among other things forpicking up landing calls and termed a landing call finder potentiometer.Such potentiometer designated LFP is located on the control panel 18 inthe pent house. The other advancer potentiometer is utilized in pickingup car calls and is termed a car call finder potentiometer. Suchpotentiometer, designated CFP, is located on the elevator car. Furtherdescription of such apparatus will be given along with the descriptionof the control circuits.

The invention will be described as applied to a system in which the caris provided with an attendant or in which no attendant is provided. Onwith attendant operation, the doors are closed and the car started inresponse to a start control operated by the car attendant. Forconvenience, it will be assumed that on without attendant operation, thedoors are closed and the car started in response to calls registered bythe passengers themselves, although it is to be understood that thelatter operation contemplates closing the doors and starting the carfrom terminals by a dispatching system, with the door closmg andstarting operations at intermediate fioors takir 1g place automaticallyupon expiration of the door time interval.

The car is provided with a car operating panel on which are located aplurality of control switches for op oration by the passengersthemselves on without attendant operation and for operation by the carattendant on with attendant operation. These switches include amongothers a plurality of push buttons, one for each floor above the lowerterminal, hereinafter termed car buttons, for registering car calls forboth without attendant operation and with attendant operation and astart control button for with attendant operation.

The car buttons are designated C and have numerals appended thereto asindicative of the floors for which the car buttons are provided.

Controls are provided at the floors to enable intending passenges toregister landing calls, an up control and a down control D beingprovided at each intermediate floor, one control D at the top terminalfloor and one control U at the bottom terminal floor. Differentiationbetween these controls is had by appended reference charactersindicative of the floors. These call registering controls willhereinafter be termed landing buttons. Hall lanterns are also providedat the landings. The hall lanterns are designated HL and differentiatedby reference characters corresponding to the floors for which they areprovided and by the letters U and D, in accordance with whether up ordown hall lanterns.

To facilitate disclosure of an application of the invention, the controlsystem illustrated has been extremely simplified as compared withcontrol systems utilized in commercial installations. It is to beunderstood that in applying the invention to control systems usedcommercially, many changes may be made, especially in adapting theinvention to the more comprehensive circuits and to control features andapparatus not here shown.

The electromagnetic switches employed in the system illustrated aredesignated as follows:

A Start and stop switch DD Down direction switch DG Direction holdingswitch EA First speed switch EAX First speed switch timing relay EBSecond speed switch EBX Second speed switch timing relay EC Third speedswitch ECX Third speed switch timing relay EX Auxiliary speed switch FFloor switch FL Late call floor switch GK Notch back switch H Brake andfield switch HI Highest call switch HR Highest call reversal switch SMStart and stop control switch UD Up direction switch Throughout thedescription which follows, these letters will be applied to the coils ofthe above designated switches. Also, with reference numerals appendedthereto, they will be applied to the contacts of these switches.

The circuits are shown in straight, i. e., across-theline, form in whichthe coils and contacts of the various switches are separated in suchmanner as to render the circuits as simple and direct as possible. Therelationship of the coils and contacts may be seen from Figure 6 whereinthe switches are arranged in alphabetical order with the coils andcontacts of the various switches positioned on spindles in alignmentwith their positions in the wiring diagram. Numbers following dashesafter the reference characters on the spindle sheet indicate the numberof the figure in which the coil or contacts appear.

The electromagnetic switches are illustrated in deenergized condition,switches DG, GK and SM Which are of the latching type being shown inreset condition. Each of these switches has two coils, one an operatingcoil and the other a reset coil. Each of switches A, BA, BB and EC hastwo coils, one an operating coil and the other a hold-in coil.

Referring to the landing call registering circuits of Figure 3, each ofthe landing buttons in the preferred arrangement comprises an electronictube and a fixed button connected to the tube envelope with the circuitsarranged so that the tube breaks down in response to manual touch of thefixed button and remains conductive, thereby registering the call andenabling the touch to be dlscontinued. These electronic tubes are coldcathode gas tubes, the type having a wire anode extending to within ashort distance of the glass envelope of the tube, such as the RCA 1C2l,having been found satisfactory. With such a tube, the button TB, seelanding button D3, is connected to the tube envelope adjacent the anode.RUL and RDL are loading resistors for the tubes. The voltage values ofthe direct current supply lines for such tubes are indicated in Figure 3of the drawings, line B being the reference voltage and thus Zero. TheR. M. S.

values of the alternating current voltages indicated in Figure 3 are:

volts from AC1 to B50 volts from GR to B+70 105 volts from AC2 to B+70It is to be noted that the anodecathode circuit of the tube of eachlanding button is from line B+150 through the tube and its loadresistance to line B. The direct current voltage thus applied to thetube is not sufficient to break down the tube. However, upon anintending passenger touching the landing button, a circuit isestablished from ground GR through the secondary of transformer T1 andby Way of line B+150 to the anode of the tube and thence from the tubeenvelope by way of the body of the intending passenger back to ground.As a result, sufiicient alternating current voltage is applied betweenthe anode and the tube envelope to break down the tube. When the tubefires, it becomes illuminated to indicate that the landing call isregistered.

Each car button C when pressed is held pressed by a magnet CBM common tothese buttons. The starting button SB in the car may be provided withother contacts to effect the operation of the doors. Car positionindicator lamps are illustrated as glow discharge lamps and designatedgenerally by PC and differentiated by reference characters correspondingto the floors for which they are provided. A plurality of floor relaysare provided, one for each floor and designated 1F, 2P, 3P, 4F and TFfor the first, second, third, fourth and top floors respectively.Resistors are designated generally as R, rectifiers as V and condensersas Q.

Other electronic tubes are employed in the system.

These include tubes arranged in call pick-up and stop initiatingcircuits. Two of these tubes are provided, one for car calls designatedCC? and one for landing calls designated LCP. Also a tube is provided inthe circuits for automatically cancelling calls registered by thelanding buttons when these calls are answered. This will hereinafter betermed landing call cancelling tube and designated LCC. Also a tube isprovided in the highest call return circuits which will be termedhighest call return tubes and designated HCR. Tubes CCP, LCC, LCP andHCR are preferably cold cathode gas tubes of the RCA OA4G type. Thecontrol of an elevator car in response to electronic touch button tubesin which system tubes CCP, LCP, LCC and HCR are utilized is described indetail in the patent to Bruns No. 2,468,289 granted April 26, 1949.Tubes TA, TEA, TEE, TEC and TGK are also cold cathode gas tubes of theRCA OA4G type and are arranged in the hold-in circuits for switches A,EA, EB 1and EC and the reset circuit for switch GK respect1ve y.Referring to Figures 3, 4 and 5, the operation of startmg and stoppingthe car will first be described. The door operating circuits are notshown. The elevator hoisting motor is illustrated as a direct currentmotor, its armature being designated MA and its field winding MP. Avariable voltage direct current generator is illustrated for supplyingcurrent to the hoisting motor, the generator armature being designatedGA, its separately excited field winding GP and its series field windingGSF. Direct current for the field windings is obtained from supply linesand which also supply current for the switches of Figure 4. Withattendant operation will first be assumed, changeover switch CO beingshown for that condition. The circuits are shown for the car positionedat the first floor under which condition the car is set for upwardtravel and thus switch DG is operated and switch HR is dropped out.

To start the car, start button SB is pressed. This causes the closing ofthe doors and completes a circuit for the operating coil of switch SM.Switch SM operates to engage contacts 8M3, completing a circuit for thecoil of switch A. This switch operates to engage contacts A1 which, uponclosure of the doors and consequent engagement of car door contacts CDand hoistway door contacts HD (the hoistway door contacts beingconnected in series relation and represented by a single pair ofcontacts), completes a circuit through contacts DGl for the coils ofswitches UD and H. Switch UD engages contacts UDl and UD2 to complete acircuit for generator field winding GP for excitation of the generatorof the proper polarity for upward car travel. Switch H engages contactsH1 completing a circuit for the brake release coil BR, releasing thebrake. As a result, the car is started in the up direction.

Incident to the starting operation, contacts 8M8 also complete a circuitfor the coil of switch GK. This switch engages contacts GK3 and GK4,short circuiting portions of generator field resistance RG andseparating contacts GKS to remove the short circuit for a portion of thesection of resistance RG subject to contacts EA2. Also contacts F1engage incident to advancer operation, as will be explained later, tocomplete a circuit through contacts A1 for the coil of switch EX,causing this switch to be operated.

While the car was standing at the first floor, switches EAX, EBX and ECXwere operated, the circuit for the coil of switch EAX being throughcontacts H2, that for the coil of switch EBX being through contactsEAXl, and that for the coil of switch ECX being through contacts EBXl.Upon the starting of the car, the separation of contacts H2 breaks thecircuit for the coil of switch EAX. This switch is delayed in droppingout by the discharge of condenser Q5. Upon dropping out it engagescontacts EAX2, completing a circuit through contacts GK2 and SM10 forthe coil of switch EA. This switch operates to engage contacts EA2 toshort circuit a step of resistance RG with resultant increase in speedof the car. Switch EAX also separates contacts EAXI which breaks thecircuit for the coil of switch EBX. Thus upon the time interval providedby condenser Q6, switch EBX drops out to cause operation of switch EB toshort circuit another step of resistance RG, further increasing thespeed of the car. In a similar manner switch. EC is operated, shortcircuiting the final step of resistance RG to bring the car up to fullspeed.

Assume now that before button SE is operated to start the car, anintending passenger at the fourth floor wishing to be carried in the updirection touches up landing button U4. This causes the tube to breakdown, the circuit being through body capacity to ground, therebyapplying alternating current obtained from transformer T1 across thetube envelope and anode. As a result an up call is registered for thefourth floor. Assuming that the car gets up to full speed in a fourfloor run, as the car arrives at call pick-up distance from the fourthfloor, switch 4F operates to engage contacts 4P5, as will be seen fromlater description. This cause voltage equal to the potential drop acrossresistor RUL4 plus the potential difference between lines B and B-50 tobe applied across the control electrode and cathode of tube LCP. At thesame time switch F operates to engage contacts F4 to complete theanode-cathode circuit of tube LCP from line AC1 to line 13-50 throughcontacts EX6, FLI and SMll and the reset coil of switch SM. This tubebreaks down due to the potential applied to its control electrode. Thiscauses switch SM to be reset, picking up the fourth fioor call. SwitchSM, upon being reset, engages contacts SMl which, owing to the fact thatcontacts 4P2 are now engaged, causes lighting of the up fourth floorhall lantern UHL4.

The anode and cathode of tube LCC are connected across resistor RLCDlwhich with resistor RLCD2 forms a voltage divider connected across lines13-56 and AC2. As a result about three-quarters of the voltage acrossthese lines is applied across the anode-cathode of tube LCC. As theswitch SM is reset, contacts SM9 engage to place on the controlelectrode of tube LCC the cathode potential of tube U4. The circuit isfrom the cathode through contacts 4P5, HR6 and SM9 and the secondary oftransformer T3 to the control electrode. This potential, with thealternating current voltage from transformer T3 superimposed thereon, issuflicient to cause tube LCC to fire. This raises the cathode potentialof tube LCC to a value tube drop below the anode potential. Due toblocking rectifier VLC permitting the flow of current from the cathodeof tube LCC to the cathode of tube U4, the potential of the cathode oftube U4 is raised with respect to its anode, causing this tube to beextinguished. Thus the up call at the fourth floor is automaticallycancelled immediately the call is picked up. The cancelling of the calldrops the potential of the cathode of tube U4 to that of line B. As aresult, tube LCC is extinguished during the negative portion of thealternating current cycle and does not refire.

Switch SM, upon being reset, separates contacts SMS and engages contactsSMS, transferring the control of switch A from its operating coil to itshold-in coil, completing the circuit for the hold-in coils of switchesEA, EB and EC and breaking the circuit for the operating coil of switchGK. As will be seen from later description, under the assumed conditionsswitch GK is reset as the car arrives at a certain distance from thefourth floor and thereafter switches EC, EB and EA drop out in sequenceto gradually reduce the strength of the generator field to slow down thecar. As the car arrives at the floor switch A drops out to separatecontacts A1, breaking the circuit for the coils of switches UD and Hwith the result that the circuit for generator field winding GE isbroken and the brake is applied to bring the car to a stop.

Stopping of the car in response to a car call is effected in a similarmanner. Assume again that the car is positioned at the first floor andassume further that before the attendant presses start button SB toclose the doors and start the car, a passenger enters the car andannounces the fourth floor as his destination. The attendant thereuponpresses car button C4 which is held in by car button magnet CBM. As thecar arrives at call pick-up distance from the fourth floor, slider CFPSZof potentiometer CFP engages fourth floor contact CP4, connecting thecontrol electrode of tube CC? to line B+1S0. At the same time contactsF4 engage completing the anode-cathode circuit of tube CCP, causing thistube to break down and the reset of switch SM. As a result, the fourthfloor up hall lantern is lighted and the car is slowed down and broughtto a stop at the fourth floor.

It is believed that it will be understood from the above descriptionthat during upward travel of the car, stops are made at all floors forwhich car calls and up landing calls are registered. The car calls arepicked up upon the engagement of slider CFPSZ with the stationarycontacts C? for the floors for which car calls are regis tered and theup landing calls are picked up upon the operation of relays 1F to TF forthe floors for which such landing calls are registered.

A stop may be made during upward travel in response to a down landingcall for a floor provided no up landng call exists for that fioor and nocall exists for a floor .bove. Assume again that the car is at the firstfloor and that a down call is registered for the fourth floor. As aresult the potential drop across loading resistor RDL4 plus thepotential existing between lines B and B-50 is applied across thecontrol electrode and cathode of tube HCR by way of blocking rectifiersVD4, VI-IL3 and VHLZ and contacts 1P5, closed when the car is at thefirst floor. This causes tube HCR to be fired and as a consequenceswitch H] to be operated. Incident to the starting of the car from thefirst floor, contacts 1P5 separate and contacts F2 engage. CondenserQHCR insures maintaining switch H] in operated condition during thistransition. The same is true as the car passes the second and thirdfloors where there is transition between contacts F2 and 2P4 and 31 4.However, upon the separation of contacts F2 as the car reaches callpick-up distance from the fourth floor, the circuit to the controlelectrode of tube HCR is broken inasmuch as no up landing call isregistered for the fourth floor and no landing call is registered for afloor above so that the engagement of contacts 4P4 does not establishanother :onnection to the control electrode and inasmuch as noconnection to the control electrode is established by way of fifth floorcar button CT. As a result, switch H] drops out and enga es contactsH12. completing a circuit through contacts 8M7, EX4 and D69 for the coilof switch HR. This switch operates to separate contacts H126 and engagecontacts HRS. gagement of the latter contacts, the down fourth floorcall is picked up, the call is reset and the car is caused to be sloweddown and come to a stop at the fourth floor as above described. Also,switch HR separates contacts HRZ and engages contacts I-IRI so that acircuit is completed by way of circuits SMT and 4F]. for the down hallAs a result of the en lantern DHL4 at the fourth floor. Upon thedropping out of switch EX in the stopping operation, contacts EXF:engage completing a circuit through contacts HR?) and DG8 for the resetcoil of switch DG, causing this switch to be reset and thus set the carfor downward travel.

Switch DD is operated in response to operation of the start button whenthe car is set for downward travel inasmuch as contacts DGZ are engaged.Switch DG also engages contacts 13-610 to establish a holding circuitfor the coil of switch HR. As a result the car is maintained set fordownward travel until the first floor is reached, the operation ofswitch DG to set the car for upward travel being dependent upon theengagement of contacts IE2 and EX3 which takes place when the carreaches the first floor. It is to be understood that during the downwardtravel of the car, the car stops in response to car calls and downlanding calls. If a down landing call is registered at the second floorfor example, upon the engagement of contacts 2P3 the call is picked upand switch SM is reset, causing the car to be brought to a stop at thesecond floor. Also, the engagement of contacts 2P1 and 5M1 causes thelighting of the down hall lantern DHLZ. If instead a second floor carcall is registered, the call is picked up upon the engagement of sliderCFPSZ with contact CP2, causing the reset of switch SM and the slow downand stopping of the car at the second floor. The stopping of the car atthe first floor on its downward trip is effected by the engagement ofslider CFPSZ and stationary contact CPI permanently connected to lineB+150. The operated car buttons are released each time the direction ofcar travel is changed, due to the deenergization of the car buttonmagnet CBM by the breaking and reclosing of its circuit upon operationor reset of switch DG.

When switch CO is thrown to its upper position, both the starting of thecar and operation of switch SM is dependent upon the closing of thedoors, which in a collective control system for example is dependentupon a call being registered. The picking up of the calls and stoppingof the car, however, is the same as previously described.

Referring now to Figure 2, the potentiometers are illustrated asconnected across alternating current mains designated AC5 and AC6, takenoff main transformer MT supplied by lines L1 and L2. Each ofpotentiometers LFP, CFP and FRP is provided with tapped points whichrepresent the various floors. Connected across these tapped points ofpotentiometers LFP, CFP and FRP are resistors FHRL, FHRC and FHRFrespectively of relatively low ohmic value. Their ohmic values vary inaccordance with the height of the floors for which they are respectivelyprovided and thus fix the potential of these tapped points to be inaccordance with the heights of the floors which they represent. Thus thetapped points may be equally spaced even though the floor heights vary.The sliders of these potentiometers are actuated by motors illustratedas two phase alternating current rnotors. The armature of the motor foractuating the floor reference potentiometer sliders FRPSI and FRPSZ isdesignated ERA and its field windings FREE and PRFZ. The armature of themotor for actuating the car call finder potentiometer sliders CFPSI andCFPSZ is designated CFMA and its field windings CFMPI and CFMFZ. Thearmature of the motor for actuating the landing call potentiometersliders LFPSI and LFPS2 is designated ADA and its field windings ADFIand ADFZ. Field windings ADFl, CFMFI and FRFI are connected across linesAC5 and AC6 in series with condensers QAF, QCFM and QFR to provide fixedexcitation in phase shift relation to the excitation provided bywindings ADFZ, CFMF2 and FRF2 which is variable. Each of field windingsADFZ, CFMFZ and FRFZ is excited from the secondary of a controltransformer, the exciting voltage of which is applied to an amplifier(indicated as in block form) which is connected to the field winding.The advancer amplifier is designated AAM, the advancer amplifier inputtransformer AT2 and the advancer amplifier power transformer ATl. Thecar call finder amplifier is designated CFA, its input transformer CFTZand its power transformer CFTI. The floor reference amplifier isdesignated FAM, its input transformer FRTZ and its power transformerFRTI. ABT is the advancer biasing transformer while CPP is the carposition potentiometer, the slider of which is actuated by the car.

For convenience, the operation of the floor reference potentiometer willfirst be described. With the car positioned at the first floor asindicated by the positions of the sliders, no voltage exists betweensliders CPS and PRPSI, the connection between which represents thediagonal of the bridge formed by potentiometers CPP and FRP. As the carmoves upwardly, sliders CPS moves to the right, causing a voltagebetween sliders CPS and FRPSl which is applied to the primary oftransformer FRTZ. This voltage is amplified and applied to field windingFRFZ and is of the proper phase with respect to the excitation providedby winding FRFI to cause movement of slider FRPSl to the right. In thisway, as the car moves upwardly, slider FRPSI is caused to follow sliderCPS, substantially in synchronism with the car. When the car movesdownwardly, the excitation of winding FRFZ is reversed, causing sliderFRPSI to follow slider CPS. Thus potentiometer FRP is actuatedsubstantially in synchronism with the car. This movement may be utilizedfor various operations, being illustrated as controlling a car positionindicator, see Figure 5, where slider FRPSZ engages contacts CFPC tocause the successive lighting of lamps PC.

The operation of landing call finder potentiometer LFP will now bedescribed. Assuming with attendant operation, when start button SB ispressed to initiate starting of the car, switch SM operates to engagecontacts 8M2 and 8M4 and to separate contacts SM3 and SM6. Theseparation of contacts SM3 and reengagement of contacts 5M2 transfersthe connection of amplifier AAM from rectifiers V1 and V2 to fieldwinding ADFZ. The separation of contacts SM6 and engagement of contacts8M4 transfers the connection of the primary of input transformer AT2from floor accuracy resistor FAR to the secondary of biasing transformerABT. This causes a voltage between sliders LFPSI and CPS which isapplied through transformer AT2 and amplifier AAM to field winding ADFZ.This voltage is of a phase to cause movement of slider LFPSI to theright, thus advancing this slider with respect to slider CPS and thuswith respect to the car.

The extent of the full advance of slider LFPSI is de termined by thecharacteristics of the particular installation, especially full runningspeed. As will be seen, potentiometer LFP also controls the lighting ofthe hall lanterns. It is desirable to give sufficient advance lightingof the hall lanterns particularly in plural elevator installations toprovide time for the passenger to place himself in front of theanswering elevator, thereby avoiding loss of tlme waiting on passengers.The advance may be greater than car stopping distance but in such casethis increases chances of registering calls too late to intercept thecar. Thus the amount of advance is compromised between these two factorsand is determined by the point at which connection is made to resistorR7. For example, on installations of 500 F. P. M., this advance would be12 feet whereas on installations of 1200 F. P. M., it would be 60 feet.

As will be explained below, the advance may be halted by picking up acall before full advance is obtained. If not brush LFPSl is maintainedby the biasing voltage in full advance of brush CPS as the latter ismoved by the car. As previously explained, on with attendant operation,the advance takes place during the closing of the doors. If the doorsclose before the full advance is had, the rate of advance is set toinsure picking up of the call the desired distance in advance of thecar. This is also the case on without attendant operation where theadvance does not start until the doors reach closed position. When thecar is set for upward travel, as above assumed, contacts D64 are engagedwhich causes the phase of the biasing voltage to be such as to moveslider LFPSI to the right. When the car is set for downward travel,contacts DGS are engaged, causing the advance movement to be to theleft. Thus in each case, the advance of slider LFPSI with respect toslider CPS is in accordance with the direction of car movement.

Slider LFPSZ of the landing call finder potentiometer engages contactsLFPCL LFPCZ, etc, in succession to cause the operation and dropping outof floor relays 1P, 2P, etc. Thus upon the operation of a floor relayfor which a landing call is registered for the direction of car travel,the call is picked up to cause reset of switch SM. Thus contacts 8M4separate, removing the biasing voltage, and contacts SM2 separate todisconnect field winding ADF2, bringing the advancer motor to a stopwith slider LFPS2 in engagement with the stationary contact. Thisenables the hall lantern to be lighted and the call to be automaticallycancelled, as previously described. In this connection, switch P, whichoperates each time a floor relay is operated, separates contacts F3 todisconnect the coil of switch FL. Switch FL is delayed slightly indropping out by the discharge of condenser Q8. Upon dropping out itseparates contacts FLl, thereby preventing the establishing of the resetcoil circuit for switch SM, thus obviating picking up a late call whichmight cause the car to stop too far beyond the floor.

The slider CFPSl of the car call finder potentiometer is tied to sliderLFPSI of the landing call finder potentiometer through transformer CFTZin the same manner that slider FRPSI is tied to slider CPS, as explainedabove. As movement of slider LFPSI takes place, a voltage is applied tofield winding CFMFZ through amplifier CFA to cause operation of car callfinder motor to move slider CFPSl in step with slider LFPSI. SliderCFPSZ is moved along with slider CFPSI and engages contacts CP (Figure3) for the various floors. Upon the engagement of a contact for a floorfor which a car call is registered, switch SM is reset to remove thebiasing voltage and to disconnect field winding ADFZ to bring sliderLFPSI and thus sliders CFPSI and CFPSZ to a stop.

When switch SM is reset on picking up a landing call or car call, italso engages contacts SM6 to subject the primary winding of transformerAT2 to a voltage in an amount determined by the distance of the car fromthe floor for which the call is picked up. This voltage is obtained fromfloor accuracy resistor FAR and the amount is determined by theparticular floor relay which is operated. For example, with the car setfor upward travel, when a call is picked up at the fourth floor,contacts 4P6 are engaged to cause a voltage determined by the voltage atcontacts 4P6 with respect to the voltage at slider CPS to be applied totransformer AT2. Whereas the voltage between sliders LFPSI and CPS onlyroughly represents the distance of the car from the floor, the floorpoints on resistor FAR are accurately set, as by a galvanometer in thebridge circuit at the time of assembly. Thus a more accurate voltagemeasurement of the distance of the car from the floor at the time a callis picked up is applied to the transformer. As switch SM is reset itengages contacts 8M3 which causes this accurate voltage, amplified byamplifier AAM, to be applied to rectifier V1 and V2. Thus a directcurrent voltage, obtained from the output of these rectifiers andrepresenting the distance of the car from the floor, is applied to linesDC1 and DC2.

The direct current voltage thus obtained is applied by way of contactsSM5 in series with an alternating current biasing voltage taken offresistor R8 to resistor R6. Connections are taken off resistor R6 to thecontrol grids of tubes TA, TEA, TEB and TEC. The anode-cathode circuitsof these tubes are across lines AC5 and AC6 and include the hold-incoils of switches A, EA, EB and EC respectively. On full speed runs,contacts A2, EAl, BB1 and ECl are all engaged and maximum voltage isobtained from lines DC1 and DC2 with the result that sufficient voltageis applied across the grid-cathode of each tube to cause the tube tofire. Thus upon the engagement of contacts SM5, the hold-in coils ofthese switches are energized, it being understood that contacts SMSengage before the separation of contacts SMS to insure the holding in ofswitch A by its hold-in coil. On less than full speed runs, some ofthese switches, say switch EC, may not operate and thus will not be heldin by their hold-in coils. Also, even if operated the voltage across thegrid-cathode of the tube may be insufficient to hold it operated. Thiswill be better understood as the description proceeds.

The direct current voltage from rectifiers V1 and V2 is also applied toresistors R2 and R5 and condenser Q1. Thus the potential drop acrossthem at the instant switch SM is reset is proportional to the distanceof the car from the floor at which the stop is to be made. A biasingvoltage is taken off resistor R3, the voltage drop across this resistorbeing constant and due to the secondary voltage of transformer GKT. Thesum of this biasing voltage, the voltage drop across the upper portionof resistor R2 and the voltage drop across the upper portion of resistorR5 is applied across the cathode and grid of tube TGK, the anode-cathodecircuit of this tube being subject to the voltage of the secondary oftransformer GKT. The polarities of ti e potential drops across theportions of resistors R2 and R5 are in opposition, that obtained fromresistor R5 trying to fire the tube and that obtained from resistor R2opposing the firing. As the car approaches the floor, the voltage at theslider CPS approaches the voltage at contacts of the operated floorrelay, say contacts 4P6 for the fourth floor. As a result, the voltagedrop across resistor R2 decreases while that across resistor R5, due tothe large capacity of condenser Q1, remains substantially in accordancewith the distance of the car from the floor for which the call is pickedup. The net result is that when the car reaches a certain distance fromthe fioor, determined by the length of the run, the potential drop takenfrom resistor R2 diminishes to a point where tube TGK breaks down tocomplete the circuit for the reset coil of switch GK.

Assuming a full speed run, the reset of switch GK causes separation ofcontacts GK3 to insert a portion of resistor RG in circuit withgenerator field winding GF, initiating slowing down the car. At the sametime, contacts GK2 separate to render switches EA, EB and EC subject totheir holding coils alone. As the car approaches still closer to thefloor the potential drop across the gridcathode of tube TEC decreases toa point where the tube does not refire upon the next alternating currentcycle with the result that switch EC drops out to separate contacts EC2,inserting a further portion of resistor RG in circuit with the generatorfield winding to further slow down the car. It is to be noted that owingto the fact that contacts GK4 are separated, the amount of resistor RGthus inserted is greater than was short circuited by contacts EC2 duringacceleration of the car. As the car approaches still closer to thefloor, the potential drop across the grid-cathode of tube TEB decreasesto a point where the tube does not refire, causing the dropping out ofswitch EB. As a result, contacts E132 separate to insert a furtherportion of resistor RG in circuit with the generator field winding tocause further slow down of the car. As the car arrives at a point stillcloser to the floor, switch EA is dropped out in a similar manner toseparate contacts EA2 to further slow down the car. Due to theengagement of contacts GKS the amount of resistance inserted by theseparation of contacts EA2 is less than that which was short circuitedfor acceleration of the car. As the car arrives at the floor, switch Ais similarly dropped out causing the dropping out of switches UD and Hto break the circuit for the generator field winding and apply the braketo bring the car to a stop.

On less than full speed runs, the voltage drops across resistors R2 andR5 at the time the call is picked up is less than on full speed runs.The net result is that the distance of the car from the floor at thetime switch GK is reset is less, the shorter the length of the run. Onless than full speed runs, the reset of switch GK interrupts theacceleration of the car. Also, upon the separation of contacts GK2, onlythose of switches EA, EB and EC which are operated at the time switch GKis reset and for which there is suflicient voltage to fire their tubesTEA, TEB and TEC respectively will remain operated. This provides thedesired control of the acceleration of the car and distance control ofthe dropping out of the operated speed switches and switch A.

The arrangement whereby the difference in voltage between the voltagerepresenting the position of the car and the voltage representing thedistance of the car from the stopping floor is utilized to controlswitches GK, EC, EB, EA and A serves as a servo system for controllingthe retardation and stopping of the elevator car. The motion of theelevator car forces the car to slow down on a distance control basis andfinally to come to a stop at a fixed point, thus providing a closedcycle system. The diiference between these two voltages dictates thegenerator voltage. The generator armature and motor armature beingconnected in a loop circuit forms another closed cycle system in whichthe difference between the generator voltage and counter e. m. f. of themotor determines the speed of the motor.

Thus, it is seen that there is provided control mechanism for elevatorswhich performs electrically the functions of mechanical selectors andfloor controllers in a simple and economical manner. Also, the mechanismmay be economically manufactured and installed. Utilization of thecontrol mechanism dispenses with a considerable amount of hoistwaywiring and enables other wiring to be done at the factory. Furthermore,in a plural elevator installation, these control mechanisms for allelevators may be located together, thus simplifying the cross connectingof the circuits and enabling this wiring also to be done at the factory.

While alternating current supply lines have been illustrated for thepotentiometers, it is to be understood that direct current lines may beutilized in which event direct current amplification and motors will beemployed. Levelling mechanism has not been previously referred to, butit is to be understood that the voltage difference in the diagonal ofthe bridge formed by potentiometer CPP and resistor FAR may be utilizedfor this purpose, as by acting through amplifier AAM to operate up anddown levelling switches. Also, any one of a plurality of known levellingarrangements may be employed. If desired, conventional push buttonsacting through floor relays may be utilized instead of touch buttons forregistering landing calls.

As many changes could be made in the above construction and manyapparently widely different embodiments of this invention could be madewithout departing from the scope thereof, it is intended that all mattercontained in the above description or shown in the accompanying drawingsshall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In a control system for an elevator car serving a plurality offloors, a motor for raising and lowering the car, a voltage source, apair of resistors connected in bridge relationship across said source,one for car position reference and the other for fioor positionreference, means for moving the end of the bridge diagonal on the carposition reference resistor side of the bridge in accordance withmovement of the car, means responsive to a voltage difference acrosssaid diagonal for moving said other end of said diagonal, and means forapplying a voltage to said diagonal to cause said other end thereof toadvance a fixed amount with respect to said one end thereof incident tothe starting of the car so as to cause movement of said other end insaid advanced position with respect to said one end upon movement ofsaid one end during movement of the car.

2. In a control system for an elevator car serving a plurality offloors, a motor for raising and lowering the car, a voltage source, apair of resistors connected in bridge relationship across said source,one for car position reference and the other for floor positionreference, means for moving the end of the bridge diagonal on the carposition reference resistor side of the bridge in accordance withmovement of the car, means responsive to a voltage difference acrosssaid diagonal for moving said other end of said diagonal, means forapplying a voltage to said diagonal to cause said other end thereof toadvance a fixed amount with respect to said one end thereof incident tothe starting of the car so as to cause movement of said other end insaid advanced position with respect to said one end upon movement ofsaid one end during movement of the car, and means responsive to thearrival of the car a distance corresponding to said advance from thefloor at which a stop is to be made for discontinuing further movementof said other end of said diagonal so as to cause the advance to betaken up as the car comes to said floor.

3. In a control system for an elevator car serving a plurality offloors, a motor for raising and lowering the car, a voltage source, apotentiometer connected across said source, said potentiometer having aslider actuated by the elevator car in accordance with the movement ofthe car to register car position, a resistor connected across saidsource, said resistor having tapped points representing said floors toprovide sections of ohmic values corresponding to the heights of saidfloors, contacting means adapted to engage said tapped points when thecar is stopped at the respective floors for which such points areprovided, means responsive to the initiation of the starting of the carfor applying a biasing voltage between said slider and contacting means,means responsive to the voltage difference between said slider andcontacting means for advancing said contacting means with respect tosaid slider an amount determined by the value of said biasing voltage,and control mechanism actuated along with said contacting means forcontrolling the operation of the car.

4. In a control system for an elevator car serving a plurality offloors, a motor for raising and lowering the car, a voltage source, apotentiometer connected across said source, said potentiometer having aslider actuated by the elevator car in accordance with the movement ofthe car, a floor reference resistor connected across said source,movable contacting means for said resistor, means responsive to avoltage difference between said slider and contacting means for movingsaid contacting means, means responsive to the initiation of thestarting of the car for causing a voltage difference between said sliderand contacting means for advancing said contacting means with respect tosaid slider, thus causing said contacting means to move in advancedrelation to said slider during movement of the car, call registeringmeans for each floor, call pick-up means actuated by said contactingmeans for picking up calls which are registered, and means responsive tothe picking up of a call for stopping movement of said contacting means.

5. In a control system for an elevator car serving a plurality offloors, a motor for raising and lowering the car, a voltage source, apotentiometer connected across said source, said potentiometer having aslider actuated by the elevator car in accordance with the movement ofthe car, a floor reference resistor connected across said source,movable contacting means for said resistor, means responsive to avoltage difference between said slider and contacting means for movingsaid contacting means, means responsive to the initiation of thestarting of the car for causing a voltage difference between said sliderand contacting means for advancing said contacting means with respect tosaid slider, thus causing said contacting means to move in advancedrelation to said slider during movement of the car, call registeringmeans for each floor, means actuated by said contacting means forpicking up and then cancelling calls which are registered, meansresponsive to the picking up of a call for stopping movement of saidcontacting means, and retardation control means controlled by continuedmovement of said slider after stopping of said contacting means forcontrolling the slowing down and stopping of the car.

6. In a control system for an elevator car serving a plurality offloors, a motor for raising and lowering the car, a voltage source, apotentiometer connected across said source, said potentiometer having aslider actuated by the elevator car in accordance with the movement ofthe car, a floor reference resistor connected across said source,movable contacting means for said resistor, means responsive to avoltage difference between said slider and contacting means for movingsaid contacting means, means responsive to the initiation of thestarting of the car for causing a voltage difference between said sliderand contacting means for advancing said contacting means with respect tosaid slider, thus causing said contacting means to move in advancedrelation to said slider during movement of the car, call registeringmeans for each floor, means actuated by said contacting means forpicking up and then cancelling calls which are registered, meansresponsive to the picking up of a call for stopping movement of saidcontacting means, a hall lantern at each of said floors; and meanscontrolled by said means for stopping movement of said contacting meansfor causing lighting of the hall lantern for the floor for which thecall is picked up.

7. In a control system for an elevator car serving a plurality offloors, a motor for raising and lowering the car, a voltage source, apotentiometer connected across said source, said potentiometer having aslider actuated by the elevator car in accordance with the movement ofthe car to register car position, a resistor connected across saidsource, said resistor having tapped points representing said floors toprovide sections of ohmic values corresponding to the heights of saidfloors, contacting means adapted to engage said tapped points when thecar is stopped at the respective floors for which such points areprovided, means responsive to a voltage difference between said sliderand contacting means for moving said contacting means, means responsiveto the initiation of the starting of the car for applying a biasingvoltage between said slider and contacting means for advancing saidcontacting means with respect to said slider an amount determined by thevalue of said biasing voltage, thus causing said contacting means tomove in advanced relation to said slider during movement of the car,call registering means for each floor, and call pick-up means actuatedby said contacting means for picking up registered calls said advancedistance from the floors for which the calls are registered.

8. In a control system for an elevator car serving a plurality offloors, a motor for raising and lowering the car, an alternating currentvoltage source, a potentiometer connected across said source, saidpotentiometer having a slider actuated by the elevator car in accordancewith the movement of the car to register car position, a resistorconnected across said source, said resistor having tapped pointsrepresenting said floors to provide sections of ohmic valuescorresponding to the heights of said floors, contacting means adapted toengage said tapped points when the car is stopped at the respectivefloors for which such points are provided, means responsive to a voltagediiference be tween said slider and contacting means for moving saidcontacting means in a direction determined by the phase of said voltagediiference, means responsive to the initiation of the starting of thecar for applying between said slider and contacting means a biasingvoltage of a phase for advancing said contacting means with respect tosaid slider in the direction in which the car is to move and an amountdetermined by the value of said biasing voltage, thus causing saidcontacting means to move in advanced relation to said slider duringmovement of the car, call 'registering means for each floor, callpick-up means actuated by said contacting means for picking upregistered calls during said advance or during movement of saidcontacting means in advanced condition, and means responsive to thepicking up of a call for stopping said contacting means moving meanswith said contacting means in engagement with the tapped point for thefloor for which the call is picked up.

9. In a control system for an elevator car serving a plurality offioors, a motor for raising and lowering the car, an alternating currentvoltage source, a potentiometer connected across said source, saidpotentiometer having a slider actuated by the elevator car in accordancewith the movement of the car to register car position, a resistorconnected across said source, said resistor having tapped pointsrepresenting said floors to provide sections of ohmic valuescorresponding to the heights of said floors, contacting means adapted toengage said tapped points when the car is stopped at the respectivefloors for which such points are provided, means responsive to a voltagedifference between said slider and contacting means for moving saidcontacting means in a direction determined by the phase of said voltagediiference, means responsive to the initiation of the starting of thecar for applying between said slider and contacting means a biasingvoltage of a phase for advancing said contacting means with respect tosaid slider in the direction in which the car is to move and an amountdetermined by the value of said biasing voltage, thus causing saidcontacting means to move in advanced relation to said slider duringmovement of the car, call registering means for each floor, call pick-upmeans actuated by said contacting means for picking up registered callsduring said advance or during movement of said contacting means inadvanced condition, means responsive to the picking up of a call forstopping said contacting means moving means with said contacting meansin engagement with the tapped point for the floor for which the call ispicked up, the movement of said slider taking up said advance as the carcomes to said floor, and retardation control means controlled by thetaking up of plying a voltage to the diagonal of the the advance forcontrolling the retardation of said motor to slow down and bring the carto a stop at said floor.

10. In a control system for an elevator car serving a plurality offloors, a motor for raising and lowering the car, a voltage source, afirst resistor for providing car position reference, a second resistorfor providing floor position reference, a third resistor for providingcar position reference, movable contacting means for each resistor, saidfirst and second resistors being connected in bridge relationship acrosssaid source and said first and third resistors being connected in bridgerelationship across said source, means for moving the contacting meansfor said first resistor in accordance with movement of the car, meansresponsive to a voltage difference across the diagonal of each bridgefor moving said contacting means for the other resistor of that bridge,means for apbridge formed by the first and second resistors to causesaid contacting means for said second resistor to advance a fixed amountwith respect to said contacting means for said first resistor incidentto the starting of the car so as to cause movement of said contactingmeans for said second resistor in said advanced position with respect tosaid contacting means for said first resistor during movement of the carwhereas said contacting means for said third resistor is moved insynchronism with said contacting means for said first resistor.

11. In a control system for an elevator car serving a plurality offloors, a motor for raising and lowering the car, a voltage source, apotentiometer connected across said source, said potentiometer having aslider actuated by the elevator car in accordance with the movement ofthe car, a first floor reference resistor connected across said source,a second floor reference resistor connected across said source, movablecontacting means for each of said first and second resistors, meansresponsive to a voltage difference between said slider and firstresistor contacting means for moving said first resistor contactingmeans, means responsive to a voltage difierence between said firstresistor contacting means and said second resistor contacting means 'formoving said second resistor contacting means, thus tying them together,means responsive to the initiation of the starting of the car forcausing a voltage difference between said slider and first resistorcontacting means for advancing said first resistor contacting means andthus also said second resistor contacting means with respect to saidslider, causing both said contacting means to move in advanced relationto said slider during movement of the car, landing call registeringmeans for each floor, landing call pick-up means actuated by said firstresistor contacting means for picking up landing calls which areregistered, car call registering means for each floor, car call pick-upmeans actuated by said second resistor contacting means for picking upcar calls which are registered, means responsive to the picking up of acall for stopping movement of both said contacting means, and meanscontrolled by continued movement of said slider after stopping of saidcontacting means for slowing down and stopping the car at the floor forwhich the call has been picked up.

References Cited in the file of this patent UNITED STATES PATENTS1,970,304 Graham Aug. 14, 1934

